The invention relates to the field of machine elements for designing a composite of two parts, and in particular, to composite of which one is a rare-earth permanent magnet and the other is a metallic support.
In a known composite of this type (DE 195 38 468 A1), a first part in the form of a cuboid permanent magnet is screwed onto a second part in the form of a cylindrical axle of a magnetic clutch. An epoxy resin-based glue which has a dual curing mechanism is used for this.
The invention is based on the discovery that such a glue is not, however, suitable for the permanent bonding of certain large-surfaced parts, such as e.g. a rare-earth permanent magnet and an iron pole of an electrical machine, because the thermomechanical property level of the epoxy resin glue is not matched in such a way, to the opposed thermal expansion coefficients of the elements to be used, that the elasticity of the bond produced in this way could meet the extreme requirements which exist whenever two glued parts with an opposed thermal expansion coefficient are used in a temperature range of from xe2x88x9230xc2x0 C. to 150xc2x0 C. Such conditions are encountered, for example, in permanent-field synchronous motors for the propulsion systems of ships (Jahrbuch der schiffbautechnischen Gesellschaft [Shipbuilders"" yearbook] 81 (1987), pp. 221 to 227). Depending on the size of the glued permanent magnets, and therefore on the size of the joint surface, thermally induced length-change differences between the glued parts of up to a few hundred xcexcm can occur; the elasticity of the glued point or bond should permit such length-change differences.
In one embodiment of the invention, there is a composite having two parts. The composite being formed using a thermally curable glue that forms a spaced joint which includes for example, a rare-earth permanent magnet having a joint surface of at least 1000 mm2 and a metallic support which is a ferromagnetic pole of an electrical machine. The glue includes an addition-crosslinking, single-component and self-adhesive silicone glue, the glue layer having a layer thickness of about 70 to 150 xcexcm and includes spherical spacers in an amount of about 0.5 to about 5% by weight of the glue mass.
In one aspect of the invention, the diameter of the spacers and a thickness of the glue layer is between about 100 and about 125 xcexcm.